Cream together butter and sugar. Add eggs and vanilla. In a separate bowl, whisk together baking powder, salt, cocoa and flour and slowly add to wet mix until fully combined. Dough will be very stiff. Roll out on a lightly floured surface to 1/8" to 1/4" thick and cut out with cookie cutters dipped in flour to prevent sticking. You can knead and re-roll out the leftover dough at least once (after that it might start to get a bit tough) to get the maximum amount of cookies. Bake at 375 F for 7 minutes. Let cool completely and frost (I used the "creamy decorating icing" from the Joy of Cooking, and could have done with maybe a half recipe of the icing).